Re: Understanding PDE information

[George Lolos <George.Lolos@uregina.ca>]

Hi Richard:

You bring very good issues so let me try to clarify here.

The Photonique (CPTA) devices are not primitive by any means.  If one 
calls them primitive it only reflects their inability to provide large 
batches that all exhibit the same breakdown voltage and this has to do 
with the Si wafer treatment, not standard CMOS.  This does not matter 
for small SiPM's that will be driven individually but for large area 
SiPM's and for hundreds or thousands, it becomes a practical issue.  
Ditto for Hamamatsu.  One side benefit of that type of Si treatment is 
that it results in lower dark current and this is what also happened to 
SensL when they moved from that treatment to CMOS, they went from DR as 
low as 200 Hz/pixel to over 1kHz/pixel and are now bringing it down. 

On the issue of the PDE, you hit the nail on the head.  The devices 
we're getting to try from SensL, mostly 3mm x 3mm but also one 1mm2, are 
R&D steps toward the large array where they investigate Si process 
treatments, trenching, optimization of pixel size to DR and linearity 
etc, etc.  The C20 is not the type the sensor arrays will be made from.  
It's much easier for any firm to produce large PDE and fill factors if 
they know that only 2mm x 2mm size will be produced and it's a whole 
different ball game to know that you're aiming at 1.25 cm x 1.25 cm.  
Carl has other 3 mm x 3mm  SiPM's from SensL with huge fill factors that 
work well but at -20 C.

I hope this clarifies where we are, what we will get and why we see such 
results now.

George


Richard Jones wrote:

> Elton and all,
>
> I have created a page on the wiki (under main page, link "Silicon 
> Photomultiplier Performance") to record this conversation, because I 
> think things are starting to become clearer.  Please look at my new 
> section added at the end, in particular my final paragraph quoted below.
>
>     If one wants to compare the Sensl and Photonique devices, it is
>     only fair to compare them under the same operating conditions:
>     1.5V over threshold. From Carl's measurements, the actual
>     efficiency of the Sensl C20 device is about 5% [he measured 4.4%
>     at 1.2V overbias, so I round up to 5% at 1.5V] compared with 24%
>     for the 2 mm Photonique device under the same conditions. _The
>     factor of 5_ in PDE between the Sensl and Photonique devices can
>     only be explained by the supposition that Sensl never intended
>     their C20 device to be considered for scintillator readout.  Nor
>     should 12% @ 500 nm be considered acceptable, given that
>     commercial devices from Photonique exist with a factor 2 larger
>     PDE.  We have heard that CPTA technology is primitive, and that
>     may be so, but then it should not be difficult to reproduce their
>     performance in these new devices from Sensl.
>
> Richard Jones
>
>
>